Vapor chamber

ABSTRACT

A vapor chamber is provided which includes a container including a first region which is heated and a second region which dissipates a heat and having a plate shape, and a working fluid which is encapsulated inside the container. The working fluid is evaporated by a heat transferred to a first region, after a vapor which is an evaporated working fluid flows to the second region, the heat is dissipated and the vapor is condensed, and the working fluid which is the condensed vapor is circulated to the first region.

CROSS REFERENCE TO RELATED APPLICATIONS

Priority is claimed on Japanese Patent Application No. 2015-069284, filed on Mar. 30, 2015, the contents of which are incorporated herein by reference.

BACKGROUND OP THE INVENTION

1. Field of the Invention

The present invention relates to a vapor chamber which transports heat as latent heat of condensation of the working fluid.

2. Description of Related Art

A heat transport device which transports heat as latent heat of working fluid is described at Japanese Unexamined Patent Application, First Publication No. 2010-151353. The heat transport device has a structure in which a laminate body is arranged in a thin plate-like container where the working fluid is encapsulated. The laminate body includes a mesh member for a gas phase that is a flow path of the vapor working fluid, and a mesh member for a liquid phase that is laminated to the mesh member for a gas phase and that makes the liquid-phase working fluid circulate from a condensing portion to an evaporating portion by generated a capillary force.

A heat transport device described in Japanese Unexamined Patent Application, First Publication. No. 2010-151355 can be used for cooling electronic devices as described. Since electronic devices generally have a structure that accommodates a large number of electronic components in a limited space. It is desirable that components for cooling are also small or as thin as possible.

However, since the heat transport device described in Japanese Unexamined Patent Application, First Publication No. 2010-151355 has a configuration using a mesh member having the stacked structure. It is difficult to make the device thin and compact. In addition, since working fluid is heated, evaporated, and condensed by heat dissipation, the internal pressure of the heat transport device increases or becomes negative. Therefore, although a structure which can withstand the changes in the internal pressure is required, conventionally, no technique for achieving both thickness or size reduction and strength there is room to develop technologies.

The present invention has been made in the above circumstances, and provides a vapor chamber which can be thinner without deteriorating the thermal transport properties and yet which is advantageous for maintaining the strength thereof.

SUMMARY OF THE INVENTION

A first aspect of the present invention is a vapor chamber including, a container including a first region which is heated and a second region which dissipates a heat and having a plate shape, and a working fluid which is encapsulated inside the container. The working fluid is evaporated by a heat transferred to a first region, after a vapor which is an evaporated working fluid flows to the second region, the heat is dissipated and the vapor is condensed, and the working fluid which is the condensed vapor is circulated to the first region. The container comprises a first plate member and a second plate member which configures a pair of plate members joined to each other with a predetermined interval. In the first plate member, an elongated protruding portion which protrudes toward the second plate member and a recess portion which recesses with respect to the second plate member and is away from the second plate member are formed. The elongated protruding portion and the recess portion is formed from the first region to the second region. A gap portion is formed between the elongated protruding portion and the second plate member, the gap portion is a liquid flow path where the working, fluid is held and flows by a capillary force due to a generation of a meniscus by entering of the working fluid, and the recess portion is a vapor flow path where the vapor flows.

In a second aspect of the present invention according to the vapor chamber of the first aspect described above, a plurality of the elongated protruding portions may be provided radially from a first region where the working fluid is evaporated.

In a third aspect of the present, invention according to the vapor chamber of the first aspect or the second aspect described above, the working fluid, may be water, and a hydrophilicity of a distal end surface of the elongated protruding portion that faces the second plate member and a portion of the second plate member that faces the distal end surface may be higher than a hydrophilicity of an inner surface of the recess portion and a portion of the second plate member that faces the recess portion.

In a fourth aspect of the present invention according to the vapor chamber of any one of the first aspect to the third aspect described above, at least the first plate member in the pair of the plate members may comprise a clad material comprising copper and stainless steel, a surface layer of the first plate member may be copper, and the copper may be exposed to an inner side of the container.

In a fifth aspect of the present invention according to the vapor chamber of any one of the first aspect to the fourth aspect described above, a projection which is in contact with the second plate member may be formed at the first plate member, and the projection may be joined on the the second plate member.

In a sixth aspect of the present invention according to the vapor chamber of any one of the first aspect to the fifth aspect described above, the first plate member may be deformed in a concave-convex shape with the elongated protruding portion and the recess portion, and in the second plate member, a first surface which is opposite to a surface facing the first plate member may be a flat surface.

According to the above-described aspects of the present invention, between the pair of plate members joined together, the gap portion between the elongated protruding portion and the second plate member and the space portion defined by the recess portion are formed, and the working fluid is encapsulated in the gap portion and in the space portion. The gap portion forms a meniscus by the influx of the liquid-phase working fluid, and the liquid-phase working fluid is held and flows in the gap portions by the capillary force due to the meniscus. Therefore, the gap portion defines a liquid flow path which allows the the liquid-phase working fluid return to an area where the evaporation of the fluid occurs and the gap portion functions as a wick since the capillary force is generated in the gap portion. Accordingly, since a wick material does not need to be placed inside the container, it is possible to obtain a thin vapor chamber. In addition, since the elongated protruding portion functions as a reinforcing rib, it is possible to provide a vapor chamber which is excellent in a bending strength.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially broken plan view showing an example of a vapor chamber according to the present embodiment.

FIG. 2 is a sectional view viewing from the II-II line of FIG. I.

FIG. 3 is a partial sectional view showing an enlarged view of one of the gap portions which is a liquid flow path.

FIG. 4 is a plan view showing a portion of a vapor chamber of another example.

FIG. 5 is a partial sectional view showing a portion of a vapor chamber of another example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention is described. FIG. 1 shows a partially broken view of a vapor chamber 1 according to the present embodiment. The vapor chamber 1 is provided with an airtight container 2, and inside the container 2, condensable working fluid is encapsulated in a state where a non-condensable gas such as air is degassed. The container 2 is formed by joining a pair of plate members 3 and 4 in a state in which a predetermined interval is provided. The plate members 3 and 4 in the example shown in FIG. 1 have a square shape or a rectangular shape and are joined in an airtight state at each of the peripheral portions. The plate members 3 and 4 are clad materials where copper and stainless steel are joined, and the clad material can have a two-layer structure of copper and stainless steel or a three-layer structure in which stainless steel is sandwiched between copper. When each of the plate members 3 and 4 is a clad material, the plate members 3 and 4 are joined so that each surface of copper is opposed to each other; therefore, the copper is exposed to an inner side of the container 2. An appropriate joining means may be employed such as welding or diffusion bonding.

The upper surface 5 of the first plate member (hereinafter, referred to as a bottom plate) 3 is spaced from the second plate member (hereinafter, referred to as the top plate) 4, and a plurality of elongated protruding portions 6 are formed on the upper surface 5 so as to protrude toward the lop plate 4. Therefore, in the upper surface 5, portions other than the elongated protruding portions 6 are separated largely from the top plate 4 and are recessed relative to the elongated protruding portions 6. In addition, the elongated protruding portions 6 are formed radially from the center portion of the upper surface 5.

FIG. 2 is a sectional view viewing from the II-II line of FIG. 1. The elongated protruding portion 6 extends radially, one end thereof corresponds to a circumferential location of a circle having a predetermined radius from a center of the upper surface 5, and the other end is located at an inner side (a location closer to the center) than the peripheral portion, which is joined to the top plate 4. A portion between these elongated protruding portions 6 is a recess portion 7 which is largely apart from the top plate 4. Since one end of the elongated protruding portion 6 is located on the circumference of the circle and each one end of the elongated protruding portion 6 is separated from the other one ends, and the other end remains at an inner side than the peripheral portion, the recess portions 7 are communicated with each other at the center portion and the peripheral portion of the upper surface 5. In the following description, the space which allows the recess portions 7 to communicate each other and is closer to the center is referred to a center-side communication portion 8, and the space which allows the recess portions 7 to communicate each other and is at the peripheral portion is referred to a communicating groove portion 9. On the other hand, the top plate 4 is a simple flat shape and an outer surface (an opposite surface of an inner surface 13 of the top plate 4) 16 of the container 2 is a flat surface.

The bottom plate 3 and the top plate 4 are joined in an airtight state, and a working fluid is encapsulated in a state in which degassing of the non-condensable gases such as air. The working fluid is a fluid that transports heat in the form of latent heat, and water, alternatives for chlorofluorocarbon, alcohol and the like can be used. In the examples shown in FIGS. 1 and 2, water is encapsulated as the working fluid.

The gap portion 10 between the elongated protruding portion 6 and the top plate 4 are described.

As shown in FIG. 3, the gap portion 10 is a liquid flow path where the liquid-phase working fluid 11 enters and thereby, a meniscus is generated and a capillary force is generated, and by the capillary force, the liquid-phase working fluid 11 flows and is held. In order to have such a function, a distance L between a distal end surface 12 of the elongated protruding portion to and the inner surface 13 of the top plate 4 that faces a distal end surface 12 is for example, 0.1 mm, or a measurement error or a processing error are added to 0.1 mm. The thickness t₄ of the top plate 4, the thickness t₃ of the bottom plate 3, and the height h₆ of the elongated protruding portion 6 are respectively 0.1 mm, or a measurement error or a processing error are added to 0.1 mm. As an example, a depth D₇ of the recess portion 7 (i.e., a distance between the bottom surface and the top plate 4 in the recess portion 7) D₇ is 0.2 mm, or a measurement error or a processing error are added to 0.2 mm, and the thickness of the vapor chamber 1 is approximately 0.4 mm.

In the gap portion 10 between the elongated protruding portion 6 and the top plate 4, in order to make the working fluid 11 enter and flow, hydrophilicity between the distal end surface 12 of the elongated protruding portion 6 and a portion 13 a in the inner surface 13 of the top plate 4, the portion 13 a facing the distal end surface 12 and being referred to as an opposing portion hereinbelow, is higher than hydrophilicity in portions other than the opposing portion 13 a. More specifically, on the distal end surface 12 and the opposing portion 13 a, the hydrophilic treatment such that a wet angle is for example, approximately 90 degree is applied. The hydrophilic treatment may be, for example, a roughening treatment such as sandblasting, etching, or the like and silver coating. In contrast, in a portion facing the recess portion 7 in the inner surface of the recess portion 7 and the top plate 4, a water repellent treatment such that a wet angle is for example, approximately 90 degrees is applied. The water repellent treatment, may be coating or applying of a fluorine resin or silicone oil. Thus, regarding the recess portion 7, since the working fluid 11 is eliminated and a cross-sectional area is wider than the gap portion 10, the recess portion 7 is a vapor flow path where the vapor of the working fluid flows.

The vapor chamber 1 shown in FIGS. 1-3 is configured by assuming the use such that a center portion of the top plate 4 is in contact with an object to be cooled which is not shown. Accordingly, a region shown by a broken line in FIG. 1 is an evaporator 14 where the heat is transferred from the outside to evaporate the working fluid 11. An outer portion of the evaporator 14 is a condenser where the vapor of the working fluid dissipates the heat and is condensed.

The operation of the above-described vapor chamber 1 is described. When the heat of the object to be cooled is transferred to the evaporator 14, the working fluid 11 evaporates due to the heat. When the working fluid 11 evaporates in the gap portion 10 which is the liquid flow path, a capillary force is generated since a meniscus is reduced. The capillary force acts as a pumping force with respect to the working fluid 11 held in the gap portion 10. Therefore, the working fluid 11 flows to a side of the evaporator 14 through the gap portion 10 as the flow path. In other words, the working fluid 11 is circulated.

The vapor of the working fluid spreads out in the recess portion 7, and flows to an area which has a low temperature and pressure in the container 2 using an inner portion of the recess portion 7 as a flowing path. Each recess portion 7 is defined by the working fluid 11 which is held in the gap portion 10 of the elongated protruding portion 6 and the distal end face 12 thereof. However, since each recess portion 7 communicates through the center-side communication portion 8 and the communicating groove portion 9 at the periphery of the container 2 described above, the internal pressure of each recess portion 7 is uniform. In other words, the vapor of the working fluid spreads throughout the inside of the container 2. In a portion having a low temperature at the periphery of the container 2 which is a condenser, the heat of the vapor of the working fluid is dissipated to the outside of the container 2 and the vapor of the working fluid is condensed.

The working fluid 11 by condensation becomes liquid droplets inside the recess portion 7 since the water-repellent treatment is applied to the inner surface of the recess portion 7. In contrast, since the hydrophilic treatment is applied to the inner surface of the gap portion 10 and a capillary force is generated, the liquid droplets of the working fluid 11 is sucked or induced in the gap portion 10 and held in the gap portion 10. In the gap portion 10, the working fluid 11 is circulated to the evaporator 14 by the pumping force generated at an area of the evaporator 14 described above.

The above-described vapor chamber 1 according to the present embodiment, a capillary force is generated in the gap portion 10 formed between the elongated protruding portion 6 and the top plate 4 and the working fluid 11 is circulated to the evaporator 14 using the gap portion 10 as a flow path. Therefore, since there is no need to place a wick material inside the container 2, it is possible to reduce the thickness of the vapor chamber 1 by configuring the thin container 2.

In addition, the bottom plate 3 is bent (molded) in a concave-convex shape in the thickness direction so as to form the elongated protruding portions 6 and the recess portion 7, and since each elongated protruding portion 6 functions as a rib, the vapor chamber 1 having a high strength can be provided. With the vapor chamber 1, although not shown, heatsinks for heat dissipation of electronic components which are objects to be cooled are brought into contact.

In the above-described vapor chamber 1 according to the present embodiment, since the top plate 4 is formed in a flat shape, an adhesiveness of the object to be cooled becomes favorable, and it is possible to reduce the thermal resistance between the top plate 4 and the object to be cooled. The vapor chamber 1 described above may be used in portable electronic devices such as a smart phone. In this case, a heat generating element such as a CPU is brought into close contact with an area corresponding to the the evaporator 14 of the top plate 4, and a heat dissipation portion such as a battery or a case and a display panel or a heat sink is in contact with the lower surface of the bottom plate 3. As shown in FIG. 2, for example, in the lower surface of the bottom plate 3, since a portion corresponding to the elongated protruding portion 6 is recessed toward the inner side of the container 2, the portion is not in contact with the heat dissipation portion. However, in the vapor chamber 1 described above, the heat is transferred radially toward the periphery portion from the center portion, and an area where the vapor of the working fluid dissipates the heat and is condensed is wide. Therefore, an area of the surface where a lower surface of the bottom plate 3 and a heat dissipation portion are in contact and the heat is transferred therebetween is wide, and the heat transfer with respect to the heat dissipation portion is not impaired.

In addition, the vapor of the working fluid flows in an inner side of the recess portion 7 used as a flow path from the evaporator 14 to the other areas having lower pressure. Therefore, regardless of the orientation or the position of the container 2, the vapor of the working fluid is allowed to flow. Furthermore, since the working fluid 11 circulates using a capillary force generated in the gap portion 10 at the side of the evaporator 14 as a pumping force, the working fluid 11 flew back to the evaporator 14 although affected by gravity depending on the orientation or the posture of the container 2. In other words, even when the container 2 is held in a slate where the bottom plate 3 and the top plate 4 is vertically inverted from a state show in FIG. 2 or in a state where the bottom plate 3 and the top plate 4 are standing in a vertical direction, a flow of the vapor of the working fluid and a circulation of the the working fluid 11 are smoothly performed. Therefore, the vapor chamber 1 according to the present invention is used in a portable electronic device which is held in various orientations or postures when carried, and can appropriately reduce the temperature of the heat spot.

The present invention is not limited to the embodiment described above, and may have the structure shown in FIGS. 4 and 5.

Whereas the vapor chamber 1 of the above-described embodiment dissipates heal radially, in the examples shown in FIGS. 4 and 5, the vapor chamber is configured to transport heat linearly from one-end area to the other-end area of the container 2. Therefore, the elongated protruding portion 6 and the recess portion 7 are formed so as to be parallel to each other and be directed along the longitudinal direction of the container 2, and the projection 15 for fastening is further provided that connects the bottom plate 3 and the lop plate 4.

The bottom plate 3 and the top plate 4 are joined together at their periphery, and at the bottom plate 3, multiple elongated protruding portions 6 which protrude toward the top plate 4 are formed parallel to one another. A portion between each of the elongated protruding portions 6 is the recess portion 7. An end portion of the elongated protruding portion 6 is positioned inner side (near the center) from a peripheral portion where the bottom plate 3 and the top plate 4 are joined. Therefore, a portion between the end portion and the peripheral portion of the elongated protruding portion 6 form a communication groove portion 9 which communicates the respective recess portions 7 each other. A gap portion 10 between a tip face 12 and the top plate 4 of the elongated protruding portion 6 is configured similarly to the gap portion 10 in the example shown in FIGS. 1 to 3 described above, and functions as a wick which generates a capillary force and forms a How path of the working fluid 11.

In the bottom plate 3, at a position corresponding to the recess portion 7, a projection 15 for fastening is formed. In the examples shown in FIGS. 4 and 5, a projection 15 is a conical protruded portion projecting toward the top plate 4, and a tip thereof is in contact with the top plate 4. The projection 15 is joined to the top plate 4 by spot welding or the like. In other words, the bottom plate 3 and the lop plate 4 are joined at their periphery and are joined to each other through the projection 15 in the center portion. Therefore, in the configuration shown in FIGS. 4 and 5, even when the length or width of the container 2 is increased, the number of joints of the bottom plate 3 and the top plate 4 increases, and since positions of the joints are dispersed, a bending strength is high. In addition, it is possible to prevent deformation such as an expansion of the container 2 in the thickness direction.

In the vapor chamber 1 shown in FIGS. 4 and 5, in the container 2, a portion at a one end of the elongated protruding portion 6 and the recess portion 7 in the longitudinal direction is used as the evaporator 14, and a portion at the other end is used as the condenser. The working fluid is evaporated by the heal transferred to the evaporator 14 from the outside of the container 2, and the vapor flows to the other end of the container 2 using the recess portion 7 as a flow path. Then, the heat of the vapor of the working fluid is dissipated at the other end which is the condenser of the container 2. The working fluid 11 generated by condensation of the vapor is sucked or induced to the gap portion 10 because there is a water-repellent action at the inner surface of the recess portion 7, the distal end surface 12 of the convex section 6 and the opposing portion 13 a in the inner surface 13 of the top plate 4 have a hydrophilic property, and the capillary force is generated in the gap portion 10.

In the evaporation section 14, the meniscus is reduced since the working fluid 11 in the gap portion 10 which is the liquid flow path is evaporated, and so called a pumping force is generated. Therefore, the working fluid 11 which is sucked or induced into the gap portion 10 is circulated to the evaporator 14 through the gap portion 10. In other words, the working fluid transports heat by a linear flow so as to reciprocate between the evaporator 14 at a one-end portion of the container 2 and the condenser at the other-end portion of the container 2. Therefore, by employing an elongated shape as the container 2, it is possible to transfer heat between a cooling portion and an object to be cooled which is far away from the cooling portion. Note that the vapor chamber 1 shown in FIGS. 4 and 5 has a similar structure except for the projection 15 as the vapor clamber 1 shown in FIGS. 1 to 3 described above. Therefore, even what the structure shown in FIGS. 4 and 5 is employed, it is possible to obtain the same operations and effects as the vapor chamber 1 shown in FIGS. 1-3.

The present invention is not limited to each embodiment described above, and the elongated protruding portion 6 and the recess portion 7 may have a curved shape other than a linear shape In addition, other than forming by bending the bottom plate 3, the elongated protruding portion 6, the recess portion 7, or the projection 15 may be formed by joining an elongated member which is to be an elongated protruding portion and a lower surface of a bottom plate or by padding on a lower surface of a bottom plate.

Furthermore, an outer shape of the vapor chamber as a whole may be a suitable shape, such as an appropriate polygonal shape or a circular shape other than a square or a rectangle. In addition, the similar projection to the projection 15 shown in FIGS. 4 and 5 described above, may be formed on the vapor chamber as shown in FIGS. 1 to 3 described above. If such configuration is provided, it is possible to prevent deformation such as bending by further increasing the strength of the container 2. Dimensions provided in the above-described embodiment is an example of the present invention and do not limit the invention.

While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims. 

What is claimed is:
 1. A vapor chamber comprising: a container comprising a first region which is betted and a second region which dissipates a heat and having a plate shape; and a working fluid which is encapsulated inside the container, wherein: the working fluid is evaporated by a heat transferred to a first region, after a vapor which is an evaporated working fluid flows to the second region, the heat is dissipated and the vapor is condensed, and the working fluid which is the condensed vapor is circulated to the first region; the container comprises a first plate member and a second plate member which configures a pair of plate members joined to each other with a predetermined interval; in the first plate member, an elongated protruding portion which protrudes toward the second plate member and a recess portion which recesses with respect to the second plate member and is away from the second plate member are formed; the elongated protruding portion and the recess portion is formed from the first region to the second region; and a gap portion is formed between the elongated protruding portion and the second plate member, the gap portion is a liquid flow path where the working fluid is held and flows by a capillary force due to a generation of a meniscus by entering of the working fluid, and the recess portion is a vapor flow path where the vapor flows.
 2. The vapor chamber according to claim 1, wherein a plurality of the elongated protruding portions is provided radially from a first region where the working fluid is evaporated.
 3. The vapor chamber according to claim 1, wherein: the working fluid is water; and a hydrophilicity of a distal end surface of the elongated protruding portion that faces the second plate member and a portion of the second plate member that faces the distal end surface, is higher than a hydrophilicity of an inner surface of the recess portion and a portion of the second plate member that faces the recess portion.
 4. The vapor chamber according to claim 1, wherein at least the first plate member in the pair of the plate members comprises a clad material comprising a copper and a stainless steel, a surface layer of the first plate member is the copper, and the copper is exposed to an inner side of the container.
 5. The vapor chamber according to any claim 1, wherein a projection which is in contact with the second plate member is formed at the first plate member, and the projection is joined on the the second plate member.
 6. The vapor chamber according to any claim 1, wherein: the first plate member is deformed in a concave-convex shape with the elongated protruding portion and the recess portion; and in the second plate member, a first surface which is opposite to a surface facing the first plate member is a flat surface. 